In greek mytology, the titans were the pre-olympian gods.
Zeus and many other olympian gods were the children of the titans, and it was they who overthrew them in order to establish their own era as the dominant deities.
Not sure when the first reference in literature or etc to the titans after the fall of the classical world, but the hulking mass of machinery isn't what I generally associate with titans excluding the warhammer 40000 titans.
The reason why people might do this is probably due to the word titan and giant being associated with huge size in modern english.
Fun fact: in ancient art titans and giants were always human form, usually naked or close enough. Commonly it was rather difficult to put their size to perspective in their portrayal in art, as they were usually no bigger than the other humanoid figures that were portrayed. In the many portrayals of the gigantomachy, giants and olympian gods alike were the identical size and the giants were hybrids of beast (most commonly snake) and man.
